High density fuels from isoprene

ABSTRACT

A method for producing high density fuels from isoprene which can be produced via biosynthetic routes using biomass sugars as feedstock. This allows for the production of isoprene and isoprene-derived fuels from abundant waste materials with the potential to significantly reduce DoD carbon emissions. Embodiments of the invention describe a method for conversion of isoprene to full performance jet and diesel fuels. Isoprene can be selectively oligomerized to generate a distribution of branched chain hydrocarbons. Combination of an oligomerization catalyst with a metathesis catalyst allows for the synthesis of high density cyclic fuels with performance advantages (increased density and volumetric net heat of combustion) over conventional petroleum-based fuels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional patent application, claiming the benefit of, parentapplication Ser. No. 14/314829 filed on Jun. 25, 2014, which is anon-provisional patent application, claiming the benefit of, parentapplication Ser. No. 61/840,019 filed on Jun. 27, 2013, whereby theentire disclosures of which is incorporated hereby reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

The invention generally relates to methods of making high density fuelsfrom isoprene, and more specifically, isoprene can undergo a Diels-Aldercycloaddition reaction to generate dipentene.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a flow chart showing how high density fuels are generatedfrom isoprene, according to embodiments of the invention.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the invention, as claimed.Further advantages of this invention will be apparent after a review ofthe following detailed description of the disclosed embodiments, whichare illustrated schematically in the accompanying drawings and in theappended claims.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention generally relates to methods of making high density fuelsfrom isoprene, and more specifically, blends of branched chain, cyclicand aromatic hydrocarbons generated from isoprene.

High density fuels have the potential to improve the range, loiter time,and payload of a variety of Navy systems including jets, missiles, andUAVs. Derivation of these fuels from bio-derived isoprene will reduceNavy/DoD dependence on petroleum-based fuels and will lead to reducednet carbon emissions. Embodiments of the invention describe a selectiveprocess for the conversion of isoprene to high density fuels. A range ofhydrocarbons with both cyclic and linear structures are generated toproduce a full-performance fuel that can be tailored to either jet ordiesel engines. Isoprene is generated by a variety of plants and globalemissions of this hydrocarbon are estimated at more than 650 milliontons per year. Isoprene can also be produced via biosynthetic routesusing biomass sugars including lignocellulosic feedstocks. This allowsfor the production of isoprene and isoprene-derived fuels from abundantwaste materials with the potential to significantly reduce DoD carbonemissions. Embodiments of the invention describe a method for conversionof isoprene to full performance jet and diesel fuels. A solvent can beused to dissolve the Ziegler-Natta catalyst and control the reactionrate. Alternatively, isoprene can act as both the reactant and solvent.

Isoprene can be selectively oligomerized to generate a distribution ofbranched chain hydrocarbons. Combination of an oligomerization catalystwith a metathesis catalyst allows for the synthesis of high densitycyclic fuels with performance advantages (increased density andvolumetric net heat of combustion) over conventional petroleum-basedfuels. Complementary to this process, isoprene can undergo a Diels-Aldercycloaddition reaction to generate dipentene. Blending of linearisoprene oligomers, cyclic oligomers, and dehydrogenated oligomersincluding p-cymene allows for exquisite control of fuel properties andwill allow for the formulation of full-performance renewable jet anddiesel fuels.

The following are papers describing oligomerization of isoprene andother 1,3-dienes. The selective trimerization of isoprene with chromiumN,N-bis(diarylphosphino)amine catalysts is described in: Bowen, L. E.;Charernsuk, M.; Wass, D. F. Chem. Conimun. 2007, 2835-2837. For a reviewof catalytic oligomerization of 1,3-dienes, see Baker, R. Chem. Rev.1973, 73, 487. Cationic oligomerization of isoprene is described in:Audisio, G.; Priola, A.; Rossini, A. Makromolekulare Chemie.Macromolecular Symposia 1991, 47, 263-270. The synthesis of linearisoprene oligomers with nickel-containing homogenous catalysts isdescribed in: Dzhemilev, U. M.; Latypov, G. M.; Tolstikov, G. A.;Vostrikova, 0. S. Russian Chemical Bulletin 1979, 28, 509-512.

Embodiments of the invention include the following: (please see TheFIGURE)

1. Isoprene is allowed to react with a metallocene-based Ziegler Nattacatalyst.

2A. The resulting oligomer mixture is hydrogenated to yield a saturatedhydrocarbon mixture.

3A. The saturated hydrocarbon mixture is fractionally distilled togenerate a fuel, or

2B. The resulting oligomer mixture is allowed to react with a metathesiscatalyst to yield cyclic structures.

3B. The cyclic oligomers are hydrogenated to yield a saturatedhydrocarbon mixture.

4B. The mixture is fractionally distilled to generate a fuel.

5. Fuels prepared in step 3a and 4b can be blended to generate a fuelmixture, or

6C. Isoprene is converted to cyclic dimers by known methods.

7C. The resulting dimers are hydrogenated and blended with fuelsprepared in steps 3a, 4b, or 5, or

7D. Cyclic dimers prepared in step 6C are dehydrogenated to aromaticcompounds.

8D. Aromatic compounds prepared in 7D are blended with fuels prepared in3a, 4b, 5, or 6C.

Further embodiments of the invention include the following: (please seeThe FIGURE)

1. Isoprene is allowed to react with a metallocene-type catalyst basedon metals including, but not limited to, titanium, zirconium, hafnium,or vanadium in the presence of a co-catalyst typically comprised of analuminum alkyl compound or partially hydrolyzed aluminum alkyl (e.g.methylaluminoxane). The reaction can be carried out with or without asolvent at temperatures in the range of about −20 to about 120 degreesCelsius. In embodiments, the Al/metallocene ratio can be altered toachieve a desired distribution of oligomers. Al/metallocene ratiosbetween 1 and about 1000 are employed.

2A. The resulting oligomer mixture can be directly hydrogenated under ahydrogen atmosphere with a heterogeneous catalyst based on metals thatinclude, but are not limited to, Ni, Pd, Pt, Ru, or Cu. Pressuresbetween 0.1 and about 100 atmospheres and temperatures between ambientand about 250 degrees C. are suitable for this conversion.

3A. The resulting hydrocarbon mixture is purified by fractionaldistillation to yield a fuel product with the required propertiesincluding, but not limited to, flash point, density, and volumetric netheat of combustion.

2B. The resulting oligomer mixture from Step 1 is allowed to react witha metathesis catalyst based on metals including Ru, Mo, W, Re, or Ti.This results in ring closing metathesis (RCM) reactions to yield cyclicoligomers as shown in the supporting information.

3B. The cyclic oligomers are hydrogenated as described in Step 2A.

4B, The hydrogenated cyclic oligomers are purified by fractionaldistillation as described in Step 3A.

5. In embodiments, fuels produced in Step 3A are blended with fuelsproduced in Step 4B.

6C. Isoprene is converted to cyclic dimers by Diels Alder cycloaddition.This can be accomplished by addition of heat and/or a catalyst and ispromoted by conducting the reaction under pressure.

7C. Cyclic dimers are hydrogenated as described in Step 2A and then arecombined with fuel mixtures prepared in Steps 3A, 4B, or 5.

7D. Cyclic dimers prepared in 6C are dehydrogenated to aromaticcompounds by methods known in the art.

8D. Aromatic compounds prepared in Step 7D are combined with fuelmixtures prepared in

Steps 3a, 4B, 5, or 7C.

Embodiments of the invention generally relate to methods for convertingisoprene into fuels including, reacting isoprene with at least oneZiegler-Natta type catalyst based on first metal(s) in the presence ofat least one co-catalyst to produce an oligomer mixture of dimers,trimers, and tetramers, hydrogenating the oligomer mixture under ahydrogen atmosphere with at least one heterogeneous catalyst based onsecond metal(s) at pressures between about 0.1 atmosphere and about 100atmosphere and at temperatures ranging from about ambient to about 250°C. to produce a substantially or completely saturated hydrocarbonmixture of dimers, trimers, and tetramers, and purifying the hydrocarbonmixture by removing the heterogeneous catalyst to produce substantiallyor completely saturated fuels.

Another aspect of the invention generally relates to methods forconverting isoprene into fuels including, reacting isoprene with atleast one metallocene type catalyst based on first metal(s) in thepresence of at least one co-catalyst to produce an oligomer mixture ofdimers, trimers, and tetramers, reacting the oligomer mixture with atleast one metathesis catalyst based on second metal(s) or to producecyclic oligomers, hydrogenating the oligomer mixture under a hydrogenatmosphere with at least one heterogeneous catalyst based on thirdmetal(s) at pressures between about 0.1 atmosphere and about 100atmosphere and at temperatures ranging from about ambient to about 250°C. to produce a substantially or purely saturated cyclic hydrocarbonmixture, and purifying the hydrocarbon mixture by removing theheterogeneous catalyst to produce substantially or purely saturatedcyclic fuels.

Yet another aspect of the invention generally relates to methods forconverting isoprene into fuels including, converting isoprene by a DielsAlder cycloaddition reaction either thermally or with at least one Lewisacid catalyst at temperatures ranging from about −20° C. to about 350°C. and pressures ranging from about 1 atm to 200 atm to produce cyclicdimers, hydrogenating the cyclic dimers under a hydrogen atmosphere withat least one heterogeneous catalyst based on first metal(s) at pressuresbetween about 0.1 atmosphere and about 100 atmosphere and attemperatures ranging from about ambient to about 250° C. to produce asubstantially or purely saturated cyclic hydrocarbon mixture andpurifying the cyclic hydrocarbon mixture, or alternatively,dehydrogenating the cyclic dimers with at least one heterogeneousdehydrogenation catalyst under an inert or hydrogen atmosphere togenerate a mixture of aromatic compounds, unsaturated cyclichydrocarbons, and cyclic hydrocarbons, and purifying the mixture toproduce a pure hydrocarbon mixture.

Embodiments further include at least one solvent to dissolve theZiegler-Natta catalyst. In embodiments, the Ziegler-Natta type catalystincludes a metallocene catalyst. In embodiments, the removing theheterogeneous catalyst is by fractional distillation. In otherembodiments, the Ziegler-Natta type catalyst is a heterogeneoussupported catalyst. In embodiments, the first metal(s) is selected fromthe group consisting of, but not limited to, titanium, zirconium,hafnium, vanadium, chromium, nickel, iron, palladium, platinum, and anycombination thereof. In other embodiments, the first metal(s) isselected from the group consisting of titanium, zirconium, hafnium,vanadium, and any combination thereof.

In embodiments, the co-catalyst(s) is selected from the group consistingof, but not limited to, aluminum alkyls, partially hydrolyzed aluminumalkyls (including methylaluminoxane), aromatic borane-based anions, andany combination thereof. In embodiments, the heterogeneous hydrogenationcatalyst is selected from the group consisting of, but not limited to,palladium on activated carbon, palladium on charcoal, PtO₂, Raneynickel, copper chromite, and any combination thereof. In embodiments,the second metal(s) is selected from the group consisting of, but notlimited to, Ni, Pd, Pt, Ru, Cu, and any combination thereof. Inembodiments, the reacting isoprene with at least one Ziegler-Natta typecatalyst is based on the first metal(s) in the presence of at least onethe co-catalyst is at temperatures ranging from about −20° C. to about120° C. In embodiments, the second metal(s) is selected from the groupconsisting of, but not limited to, Ru, Mo, Re, Ti, and any combinationthereof. In embodiments, the Lewis acid catalyst(s) is selected from thegroup consisting of, but not limited to, both homogenous andheterogeneous Lewis acids based on Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Al, B, Sn, and any combination thereof. In embodiments, the cyclicdimers include dipentene(s). In embodiments, the dehydrogenationcatalyst is selected from the group consisting of, but not limited to,supported and unsupported Lewis acids, metals including Pt, Pd, Ni, Cu,Zn, Ag, Ir, Rh, Re, Ru, compounds based on these and other suitablemetals, and any combination thereof.

In embodiments, the aromatic compound(s) includes p-cymene. Inembodiments, the jet and diesel fuel blends in combinations are producedby the methods herein. In embodiments, the fuel blends combinations areproduced by the methods herein having greater than or equal to 8%aromatic compounds.

Prophetic examples are for illustration purposes only and not to be usedto limit any of the embodiments. Where a range of values is provided, itis understood that each intervening value, to the tenth of the unit ofthe lower limit unless the context clearly dictates otherwise, betweenthe upper and lower limits of that range is also specifically disclosed.Each smaller range between any stated value or intervening value in astated range and any other stated or intervening value in that statedrange is encompassed within the invention. The upper and lower limits ofthese smaller ranges may independently be included or excluded in therange, and each range where either, neither or both limits are includedin the smaller ranges is also encompassed within the invention, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

What is claimed is:
 1. A method for converting isoprene into fuels,comprising: reacting isoprene with at least one metallocene typecatalyst based on first metal(s) in the presence of at least oneco-catalyst to produce an oligomer mixture of dimers, trimers, andtetramers; reacting said oligomer mixture with at least one metathesiscatalyst based on second metal(s) or to produce cyclic oligomers;hydrogenating said oligomer mixture under a hydrogen atmosphere with atleast one heterogeneous catalyst based on third metal(s) at pressuresbetween about 0.1 atmosphere and about 100 atmosphere and attemperatures ranging from about ambient to about 250° C. to produce asubstantially or purely saturated cyclic hydrocarbon mixture; andpurifying said hydrocarbon mixture by removing said heterogeneouscatalyst to produce substantially or purely saturated cyclic fuels. 2.The method according to claim 1, wherein said reacting isoprene with atleast one said Ziegler-Natta type catalyst based on said first metal(s)in the presence of at least one said co-catalyst is at temperaturesranging from about −20° C. to about 120° C.
 3. The method according toclaim 2, further comprising at least one solvent to dissolve saidZiegler-Natta catalyst.
 4. The method according to claim 2, wherein saidZiegler-Natta type catalyst includes a metallocene catalyst.
 5. Themethod according to claim 1, wherein said first metal(s) is selectedfrom the group consisting of titanium, zirconium, hafnium, vanadium, andany combination thereof.
 6. The method according to claim 1, whereinsaid co-catalyst(s) is selected from the group consisting of aluminumalkyl compound, part hydrolyzed aluminum alkyl (includingmethylaluminoxane), aromatic borane anions, and any combination thereof.7. The method according to claim 1, wherein said heterogeneous catalystis selected from the group consisting of palladium on activated carbon,palladium on charcoal, PtO₂, Raney nickel, copper chromite, and anycombination thereof.
 8. The method according to claim 1, wherein saidsecond metal(s) is selected from the group consisting of Ru, Mo, Re, Ti,and any combination thereof.
 9. The method according to claim 1, whereinsaid third metal(s) is selected from the group consisting of Ni, Pd, Pt,Ru, Cu, and any combination thereof.